function EnemyPlane(x, y, src, size_w, size_h, speed, blood, score) {
  Plane.call(this, x, y, src, size_w, size_h, speed)
  this.speed = speed;
  this.blood = blood;
  this.score = score;
  this.timer = null;
  this.init();
  this.towardDown();
  this.collision = false;
}

EnemyPlane.prototype = new Plane();
EnemyPlane.prototype.constructor = EnemyPlane;

EnemyPlane.prototype.towardDown = function () {
  this.timer = setInterval(() => {
    this.collideBullet();
    if (this.y > MAX_HEIGHT || this.collision) {
      this.disappear();
    } else {
      this.y += this.speed;
      this.eleNode.style.top = this.y + 'px';
    }
  }, 1000 / 60);
  this.y += this.speed;
  this.move();
}
EnemyPlane.prototype.disappear = function () {
  this.destory();
  enemyPlaneArray.remove(this);
  clearInterval(this.timer);
}

EnemyPlane.prototype.collideBullet = function () {
  var bulletArray = player.bulletArray;
  for (var item of bulletArray) {
    if (item.x + item.size_w > this.x && item.x < this.x + this.size_w
      && item.y < this.y + this.size_h) {
      this.blood -= item.hurt;
      if (this.blood <= 0) {
        this.collision = true;
        player.score += this.score;
        player.kill++;
        renderStatistic(player.score, player.kill, player.blood);
      }
      item.disappear();
    }
  }
  if (player.x + player.size_w > this.x && player.x < this.x + this.size_w
    && player.y < this.y + this.size_h && player.y + player.size_h > this.y) {
    if (player.died) { return; }
    player.collide();
    this.collision = true;
    renderStatistic(player.score, player.kill, player.blood);
  }
}